In the case of wind turbines, the transmission is lubricated with a lubricating medium, in particular with oil, to adjust the rotor and generator speed. The rotor shaft of the wind turbine rotor is typically mounted with a rotor bearing designed as an anti-friction bearing in a housing of the wind turbine. Lubrication is also provided for this rotor bearing by a lubricating medium, for example in the form of an oil. Because of the different requirements that must be placed on the lubricating media for the transmission and the rotor bearing, such as the viscosity and the optimum operating temperature, independent devices are used for lubrication for each of the two lubrication circuits in known wind turbines.
Since less heat is generated in the rotor bearing compared to the transmission, and cooling is effected by the large surface of the bearing housing, the rotor bearings run at lower operating temperatures, for example in the range of 10° C. to 40° C., while the transmission frequently reaches operating temperatures of 50° C. to 80° C. For technical reasons related to lubrication, lubricating media with a high viscosity are used for the rotor bearing. However, in the case of low ambient temperatures, for example in the winter, the operating temperature of the rotor bearing can drop so low that the lubricating medium, which already has a high viscosity, acquires an even higher viscosity than is useful for the optimum lubrication of the rotor bearing. To counter this higher viscosity in known systems, a heater is provided in the lubrication circuits, for example.
In the case of the transmission, on the other hand, cooling the lubrication medium is often necessary as a result of the high operating temperatures that are reached in the associated lubrication circuit to achieve the most effective possible lubrication of the transmission when the system is in operation.
Both the heating of the lubricating medium for the rotor bearing and the cooling of the lubricating medium for the transmission require devices that use energy, in particular electrical energy, during their operation.
Especially in the case of wind turbines, which from a conceptual point of view are designed to provide electrical energy, they must be designed so that their own energy consumption is kept as low as possible for the wind turbine to achieve the highest possible efficiency.
In the case of known devices for lubricating a transmission as well as a rotor bearing in a wind turbine, the transmission and the bearing are each associated with their own lubrication circuit. In each circuit, a lubricating medium flows when the device is in operation.